It is proposed to continue a comprehensive research program designed to investigate the use of electron paramagnetic resonance (EPR) as a technique for the early detection of cancer, for monitoring the progress of cancer therapy and for elucidating the nature of the free radicals involved in cancer. Detailed EPR measurements of serum ceruloplasmin will be made on blood samples from women admitted to hospitals prior to breast biopsy and compared with appropriate control levels to determine whether this technique provides a statistically reliable marker for breast cancer. EPR measurements of serum ceruloplasmin will continue to be made on blood samples obtained from patients during the course of chemotherapy to determine the statistical reliability of the measurements as prognosticators of the success or failure of the therapy. A study, based on epidemiological principles, will be initiated on EPR measurements of ceruloplasmin levels in blood obtained from male smokers 40 years of age or greater, who have accumulated at least 40 pack-years of smoking history, to determine whether the technique provides a statistically reliable marker for lung cancer. A variety of EPR techniques such as spin-labeling, ENDOR and spin-echo measurements will be applied to blood constituents to detect possible differences between the cancerous and non-cancerous state which may exist in these constituents.